Overhead electric transmission line



" Oct. 29, 1935. F. F. FowLE ET Aa.

OVERHEAD ELECTRIC TRANSMISSION LINE Filed Jan. 8, 1934J A. C. lines.

' `which has aI series Patented Oct. 29, 1935 UNITED STATES 2,019,441 novnsnnsn ELECTRIC TRANSMISSION LINE Frank F. Fowle, Winne & WireCompany, of Indiana tka, Ill., and Frederick M. Crapo, Muncie, Ind.,assignors tolndiana Steel Muncie, Ind., a corporation ApplicationJanuary 8, 1934, Serial No. 705,830

4 Claims.

Our invention relates to overhead electric transmission lines usingferrous conductors, with particular reference to A. C. transmissionlines although our invention is not limited to Our invention isapplicable, for instance, for power` lines, telephones lines, telegraphlines, signal lines, etc., and is of especial value for telephonetransmission lines; and the conductors involvedmay vbe not only thewires of the transmission circuit proper, but also include Variousancillary conductors, such as ground wires, shield wires, messengercables, catenary supports, etc., which maybe p for other than conductingpurposes and/or may actually serve to conduct current only occasionally.Therefore, by the term overhead electric transmission line" we mean anoverhead line of wire-spans under tension and which may be required tocarry electric current; and by the terms ferrous conductor orcarbon-steel conductor" we mean a conductor which may be required toserve as a currentcarrier for an electrical system and of winch thecross-section is mainly of ferrous material, specifically carbon steelin our invention, and any coating (as of zinc or copper) is a relativelysmall part of the cross-section. The term carbon steel is vused in itsacceptedY sense, (as shown by The Making. Shaping, and Treating ofSteel, by Camp and Francis, the Carnegiel Steel Company, Fourth Edition.pages 259 and '107, generally accepted as authoriphysical properties;and in which manganese is less in amount than about 1.0%, although inprevious hypoeutectoid carbon steels it has usually been greater inamount than the carbon.

It is the object of our invention to produce a transmission line ofcarbon-steel conductor (uncoated or coated as with zinc or copper) whichhas its tensile strength and its electricaly conductivity bothrelatively high. prior art an increase in tensile Generally in thestrength in ferin electrical conductivity at the cost of decreasedtensile strength; but by our invention `we are able to get bothrelatively high. The'accompanylng drawing illustrates ou'r inventiondiagrammatically. The single iigure of such drawing is a diagrammaticview of an overhead elec` tric transmission line, of ferrous conductor,in accordance with our invention, theparticular 'tra-high strength,

published by Approximate Y Approximate C. resistivity tensile strengthGrade In ohms per in pounds per mile-pound square inch Three othercommercial grades of ferrous conductors have also heretofore been usedin some lines; especially for over- These are commonly known as highstrength", and exand. named in the order of increasing tensile strengthand D. C. Approximate tensile strengths andD. C. resistivities of thesethree grades are as follows:

Siemens-MIND",

Approximate Approximate still higher tensile strength `andoften' higher.

resistivity are known as "high strength crucible and extra-high strengthp1ow; but these two grades are used infrequently. or only under somevery unusualr conditions, as for an exceptionally longpower span wherethe highest attainable wire-strength is an imperative requirementregardless of other considerations.

In all the grades known as"Siemens-Martin, high strength, extrastrength, high strength Crucible, vand extra-high strength plow", theadvantages `of increased 'tensile strength have been obtained at thesacriiice'of electrical conductivity: so that while `thete'nsilestrengths oi' such grades are substantially great- 55 'if considered atall, either was working inl the proesspf wire drawing. l

In the high-carbon ferrous conductors of the prior art of overheadtransmission, however, the high carbon content has been accompanied by ahigh contentof manganese.l This manganese content has usually exceededthe carbon content, and often exceeded it very substantially;

. and has contributed somewhat to the increase in tensile strength inthe five higher-strength grades above considered. But it has contributedmore considerably to the increase in D. C. resistivity in thesehigher-strength grades; for while such increase in D. C. resistivity hasbeen due in some measure to the content of carbon, it has been due instill greater measure to the content of. manganese.

This situation is due to the fact that the addition of carbon to alow-carbon steel of the prior art increases its tensile strength in aproportionately greater degree than the addition of an equal amount ofmanganese, but increases its D. C. resistivity in a proportionally lessdegree than th'e addition of an equal amount of manganese; and that thelelimination of manganese in a mediumcarbon or high-carbon steel such ashas been used in the prior art decreases its tensile strength inproportionately less degree than the elimination of an equal amount ofcarbon, but decreases its D. C. resistivity in proportionately greaterdegree than the elimination of an equal amount of carbon. 'p

Heretofore high manganese has in general been assumed to be necessary inany medium-carbon and higher-carbon steels used in transmission lines,`for various reasons and especially for cleansing the steel in theprocess of. manufacture;

and its etl'ect .in increasing lthe D. C. resistivity,

deemed nonseriously objectionable or wasconsidered-unavoidable. Y

In contradistinction tothe practice of the prior art, in which increasedtensile strength has apparently inevitably been accompaniedby anincrease in D'. C. resistivity; we increase the tensile strength ofoverhead ferrous conductors without correspondingly increasing the D. C.resistivity. To do this, we take advantage of the relative effects whichare producible by carbon and manganese on tensile strength and D. C.resistivity respectively, by using carbon toobtain the desired increasein tensile strength and by restrictr ing .the use of manganese andthereby avoiding in large measure the increasein D. C. resistivity. p Incarrying out do twofundamental things:

1. We provide a sufilcient carbon content in the ferrous conductor sothat the tensile strength is high-and-thesskin effect low. -As thecarbon content of ferrous material is increased, the tensile strength isalso increased, 4and at the same time the magnetic permeabilityand-therefore the y skin eflect is decreased. There is abend in theregion of 0.25% to 0.30% carbon in the curve showing rthe relationbetween carbon content of steel and skin effect, and a marked rise inskin eifect as the carbon content decreases below that region; as isshown in Eig. 'I ofPatent No.

` the Atelephone'transmissionline' forming the subour invention,therefore, we.

1,691,869 granted to one of us (Fowle) on November 13, 1928. Advantageistaken of the high tensile strength and the reduction in skin eiect bythe provision of relatively high carbon (more than 0.30%) in thesteel'of the conductors of that Fowle Patent glo. 1,691,869; and also bythe preferred provision of more than 0.25% of carbon in the ferrousconductor (coated or uncoated) of ject-matter of the co-pendingapplication of the other of us (Crapo) Serial No. 543.0%, iiled June 8,1931, now Patent No. 1,942,411, granted January i9, 1934. r

2. We keep relatively lowvthe contentof manganese. In every case We keepit below an upper limit of 0.30%, and desirably well belowV it; `for ourinyention does not require that any manganese be present. As themanganese content is lowered, it becomes possible, when so desired, toincrease the .carbon content in amounts greater proportionately thanthe. reduction in manganese, without appreciably changing the D. C.resistivity; and thus to increase the tensile strength.' ,There is nolower limit to the-manganese content from the stand-point of beneficialeffect in lowering the D. C. resistivity.

I n addition to these two fundamental things, of high carbon and lowmanganese, wealsopreferably keep the silicon content low, desirably beaspossible; for the presenceof silicon tends markedly to raise the D. C.resistivity, and our invention does"l not require the presence of anysilicon. d

, a5 Our present invention is thus concerned fundamentally with thecarbon contentv and the manganese content, and secondarily with thesilicon, content, of the general class of carbon steels.

Various other elements which may exist in caro .steel conductor (coatedor not) which is high in 45 carbon and not high inY manganese, and whichis desirably low in silicon.

In addition to this matter `of the contents of carbon and manganese, andof siliconwe may and preferably dol provide crtain'increases in 5tensile strength by heat-treatment and/or coldworking.` .That is, ourpresent invention deals fundamentally with the chemical compositionrather than withthe grainstructure of. the carbon-steel conductorinvolved, and is intended to apply generically to lgrain structures ofwhatever i sort, whether'in annealed state or in some other state suchas'may .be obtained bycertain heat treatments and/or by mechanicalworking.

Such a transmission line has the advantage of high electricalconduct'vity, for both direct currents and alternating currents,as-compared with previous ferrous transmission lines of correspondingcarbon contents. It is especiallyadvantagei ous foralternating orpulsating currents, because of the decreased' skin effect `due tothehigh carbon. At the same time, by reason of having the carbon contenthigh, and although having the content of manganese not high, we get hightensile strength. Thus we combine high tensile o strength with` highconductivity.

The carbon content of our ferrous conductor must be at least 0.25%, andis desirably at least 0.30%. It may be lconsiderably higher; but we undit desirable to keep it below the eutectoid. point, of about 0.90%. Themanganeso content 0 low 0.15% asya maximum and as much below that 1aman? 3 of our ferrous conductor must not exceed 0.30%. The siliconcontent should not exceed 0.15%.

An example of carbon-steel conductor used in our invention is a No. 12B. W. G. galvanized steel 5 wire in which the steel containedapproximately 0.41% of carbon, approximately 0,21% of manganese, andless than 0.01% of silicon. A sample of this wire was hot-galvanizedafter being annealed, and showed a D. C. resistivity of approximately5360 ohms per mile-pound, and a tensile strength of approximately 74,000pounds per square inch. Another sample of this wire was hot-galvanizedafter receiving a heat-treatment and some cold drawing, and showed a D.C. re-

sistivity of 5460 ohms per mile-pound, and a tensile strength ofapproximately 135,000 pounds per square inch. A

Another example of carbon-steel conductor used in our invention is a No.12 B. W. G. galvanized wire in which the steel contained approximately0.35% of carbon, approximately 0.20%

of manganese, and approximately 0.10% of silicon. A sample of this wirewas hot-galvanized after being annealed, and showed a D. C. resistivityof approximately 6000 ohms per mile-pound,

and a. tensile strength of approximately 72,500

pounds per square inch. Another sample of this wire was hot-galvanizedwithout being annealed,

and showed a D. C. resistivity of approximately 3o 6070 ohms permile-pound, and a tensile strength oi' approximately 120,000 pounds persquare inch.

By building an overhead transmission line of a carbon-steel conductor(coated or uncoated) conforming to the above requirements, it ispossible to have both high tensile strength and high electricalconductivity. Such a transmission line is of value for both alternatingand direct currents. and for the transmission of electric power as glias of telephone, signal, and telegraph curren It is also advantageousfor ground wires, shield 5 wires, messenger cables, catenary supports,etc.; and either as a single wire or in a stranded cable. But it is ofspecial advantage for the transmission of relativelyhigh-frequency'currents, such as those used in telephonic transmission;where 1o the frequency is voice frequency, of the order of 100 to 3000cycles per second, and the currents are usually small, not exceedingabout milliamperes.

We claim as our invention: l5

1. An overhead electric transmission line, comprising a carbon-steelconductor which is to carry current and which contains at least 0.25% ofcarbon and not in excess of 0.30% of manganese.

2. An overhead electric transmission line, com-.2o prising ahypoeutectoid carbon-steel conductor which is to carry current and whichcontains at least 0.25% of carbon and not in excess of 0.30% ofmanganese.

3. An overhead electric transmission line, com- 25 prising acarbon-steel conductor which is to carry current and which contains atleast 0.25% of carbon, not in excess o! 0.30% of manganese, and not onexcess ot 0.15% silicon.

4. An overhead electric transmission line, com- 30 prising a.hypoeutectoid carbon-steel conductor which is to carry current and whichcontains at least 0.25% ot carbon, not in excess of 0.30% oi' manganese,and not in excess of 0.15% silicon.

FREDERICK M. CRAPO.

CERTIFICATE OF CORRECTION.

Patent No. 2,019,447.

October 4'39, 1935.

FRANK F. FOWLE, ET AL.

It is hereby certified, that error appears in the above numbered patentrequiring correction as follows:

line- 26, after "and" 3, first column, line 6, for "0,21%" claim 3, for"on" read in;

in theY Patent office.

insert are; and line 50, for "extra" read 0.21%; and second and that thesaid Letters Patent these corrections therein `that the same may conformto the record of printed specification of the Page l, second column,

read `camara-high; page column, line 29, should be read with the caseSigned and sealed this 21st day of January, A. D. 1936.

Sea-l) Leslie Frazer Acting Commissioner of Patents.

aman? 3 of our ferrous conductor must not exceed 0.30%. The siliconcontent should not exceed 0.15%.

An example of carbon-steel conductor used in our invention is a No. 12B. W. G. galvanized steel 5 wire in which the steel containedapproximately 0.41% of carbon, approximately 0,21% of manganese, andless than 0.01% of silicon. A sample of this wire was hot-galvanizedafter being annealed, and showed a D. C. resistivity of approximately5360 ohms per mile-pound, and a tensile strength of approximately 74,000pounds per square inch. Another sample of this wire was hot-galvanizedafter receiving a heat-treatment and some cold drawing, and showed a D.C. re-

sistivity of 5460 ohms per mile-pound, and a tensile strength ofapproximately 135,000 pounds per square inch. A

Another example of carbon-steel conductor used in our invention is a No.12 B. W. G. galvanized wire in which the steel contained approximately0.35% of carbon, approximately 0.20%

of manganese, and approximately 0.10% of silicon. A sample of this wirewas hot-galvanized after being annealed, and showed a D. C. resistivityof approximately 6000 ohms per mile-pound,

and a. tensile strength of approximately 72,500

pounds per square inch. Another sample of this wire was hot-galvanizedwithout being annealed,

and showed a D. C. resistivity of approximately 3o 6070 ohms permile-pound, and a tensile strength oi' approximately 120,000 pounds persquare inch.

By building an overhead transmission line of a carbon-steel conductor(coated or uncoated) conforming to the above requirements, it ispossible to have both high tensile strength and high electricalconductivity. Such a transmission line is of value for both alternatingand direct currents. and for the transmission of electric power as glias of telephone, signal, and telegraph curren It is also advantageousfor ground wires, shield 5 wires, messenger cables, catenary supports,etc.; and either as a single wire or in a stranded cable. But it is ofspecial advantage for the transmission of relativelyhigh-frequency'currents, such as those used in telephonic transmission;where 1o the frequency is voice frequency, of the order of 100 to 3000cycles per second, and the currents are usually small, not exceedingabout milliamperes.

We claim as our invention: l5

1. An overhead electric transmission line, comprising a carbon-steelconductor which is to carry current and which contains at least 0.25% ofcarbon and not in excess of 0.30% of manganese.

2. An overhead electric transmission line, com-.2o prising ahypoeutectoid carbon-steel conductor which is to carry current and whichcontains at least 0.25% of carbon and not in excess of 0.30% ofmanganese.

3. An overhead electric transmission line, com- 25 prising acarbon-steel conductor which is to carry current and which contains atleast 0.25% of carbon, not in excess o! 0.30% of manganese, and not onexcess ot 0.15% silicon.

4. An overhead electric transmission line, com- 30 prising a.hypoeutectoid carbon-steel conductor which is to carry current and whichcontains at least 0.25% ot carbon, not in excess of 0.30% oi' manganese,and not in excess of 0.15% silicon.

FREDERICK M. CRAPO.

CERTIFICATE OF CORRECTION.

Patent No. 2,019,447.

October 4'39, 1935.

FRANK F. FOWLE, ET AL.

It is hereby certified, that error appears in the above numbered patentrequiring correction as follows:

line- 26, after "and" 3, first column, line 6, for "0,21%" claim 3, for"on" read in;

in theY Patent office.

insert are; and line 50, for "extra" read 0.21%; and second and that thesaid Letters Patent these corrections therein `that the same may conformto the record of printed specification of the Page l, second column,

read `camara-high; page column, line 29, should be read with the caseSigned and sealed this 21st day of January, A. D. 1936.

Sea-l) Leslie Frazer Acting Commissioner of Patents.

